An Indiana anti-abortion activist has been charged with sending a series of online death threats to Chicago-area abortion clinics, then outing himself to the FBI through a tipster line.

Luke Wiersma, 33, a member of the extremist anti-abortion group Army of God, was charged with two counts of making threats to injure another, according to a criminal complaint unsealed Wednesday in federal court in Chicago.

U.S. Magistrate Judge Sidney Schenkier ordered Wiersma, of Dyer, held without bond until a detention hearing Friday.

The FBI has been investigating a series of similar threats of violence against Chicago-area abortion clinics since at least late 2015, according to the 18-page complaint.

On Oct. 10, a clinic in Chicago received a threat through its website from someone calling himself “Luke” and using an email address that appeared to be affiliated with Army of God, according to the complaint.

“You will all f---ing pay for what you do,” the message read. “If not by my hand it will be by somebody else’s. I want you to burn, I want you all to Die.”

Three days later, the same clinic was sent a message on its website from someone claiming to be “John,” the complaint said.

“DIE, DIE, DIE,” the message read, according to the charges.

Similar threats were made to a clinic in Hammond, including one on Oct. 20 in which the poster threatened to “blow up the clinic with you and the staff in it,” according to the complaint.

“I ain’t afraid of the feds and will taunt them just to prove it,” the anonymous post to the clinic’s website read. “This ain’t nothing but a thing to me. … This is God’s retribution towards you and your kind.”

The FBI received an anonymous tip on Oct. 28 from someone claiming to live in Dyer who said Wiersma was threatening to “do whatever is necessary to stop the unmitigated murders of fetuses at baby killing mills,” according to the complaint.

“He is somebody who should be looked into,” the tipster said.

After a similar tip came in last month, the FBI obtained a warrant for the cellphone that had sent them and discovered the phone was registered to a relative of Wiersma’s, according to the complaint.

When Wiersma was taken in for questioning on Tuesday, he initially denied knowing anything about the threats. Later, he told agents, “I never intended to hurt anyone,” according to the complaint.

He then gave a videotaped statement to the FBI admitting he had sent the threats to the clinics in both 2015 and last year, according to the charges. Wiersma also admitted sending the two tips to the FBI “regarding his own criminal activity,” the complaint said.